Today, hydraulic systems are applied in multiple ways for providing large forces, for example for operating tools. Particularly tools in rescue and salvage technology, such as spreaders, presses or shears, also require the mobility of such hydraulic systems. As normally there is no power supply available at these various and undefined sites of operation, the mechanical drive of the pumps of the hydraulic systems also has to be performed by mobile drives, such as, for example, by internal combustion engines or battery-driven electric motors (DE-9412147-U).
However, especially in the case of mobile systems, high energy efficiency may be important because owing to circumstances the energy carriers used may be available only in a highly restricted manner at the site of operation. Further, when assembling the hydraulic systems and/or connecting the respective hydraulic tools to the hydraulic system, an assembly or connection as quick and simple as possible is often desired because every additionally required hand movement takes time and/or harbors other sources of errors. In rescue service in particular, there is often no time or capacity to provide for an especially efficient or low-emission operation of the rescue device. In addition, the hydraulic pump is controlled by the connected hydraulic tool in a sense that upon its actuation, the drive is raised from idle running to higher speeds.
In the prior art, this is caused by an electric switch provided on the tool (DE-9412147-U) that, however, has to be connected to the motor via a separate electric line which, however, is not desired.
In the prior art, a hydraulic controller having at least one input for a hydraulic fluid for controlling the speed of a hydraulic pump driven by an internal combustion engine has also been previously used in which the deflection of a piston, which is floatingly supported to some extent, effected by the flow of the hydraulic fluid is obtained by an electric proximity switch whereby an electric signal is output to the drive control. Thus, the speed of the internal combustion engine is changed by means of an electric servo motor via a carburetor provided on the former. Neither the failure-prone proximity switch nor the additional servo motor on the carburetor are particularly preferred in rescue because they make the devices unnecessarily complicated and are not always sufficiently robust for the tough use in emergencies.
Furthermore, the mobile hydraulic aggregates usually have at least two mutually independent hydraulic circuits. If all of these hydraulic circuits are also to be driven, at least two further disclosed controllers are required which is even less desirable.